I've had code which uses substr($foo, n, n) = ''; as an rvalue. And I'm sure others have had code which used this too. If this usage is considered a bug and Perl was resultingly changed, then this code will be broken.

Eh? Are you serious? Then, please tell, what is this snippet supposed to do? Shouldn't you have used the 4-argument substr() instead?

IMO, the value of an assignment is, commonly, what is assigned. This behaviour deviates from that generic rule in a very bizarre way: it does not return the new value, nor the old one. It just looks totally unreliable to me.

And this code wasn't written on a bug - it was written on undefined behaviour. As such, then any change to the perl implementation should be considered a core language change.

No way José. A change in previously undefined behaviour is called an improvement on the specification. You should never ever depend on undefined — or unspecified, behaviour. It is the prerogative of the Perl Porters to change that behaviour without any good reason.

And changing the behaviour so that in some way it would start to make sense, either in line with the rest in the language and returning the newly assigned value, or returning the replaced value, which would be inconsistent with the rest but which might be very handy; well: these make sense. To me, anyway.

I don't think your idiom is used that much.

In reply to Re: A Bug in the Documentation or in Perl? by bart
in thread [substr] anomaly or mine? by BrowserUk

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